For each of the reactions ,I want to save "substrate id" and all its corresponding "product id". Please help

foreach my $name(keys %($xml_hash->{reaction}} ){
         next unless name =~ m@^m:@;
         my $substrate_id = $xml_hash->{reaction}->{$name}->{substrate
+}->{id};
         my $product_id => $xml_hash->{reaction}->{$name}->{product}->
+{id};
         # do stuff here...
}
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